Fixed bird proof gap



Oct. 11, 1960 E. J. LEHMAN FIXED BIRD PROQF GAP Filed Jan. 20, 1958 mm mwk V 8 m4 8 m W 5 ATTORNEY United States Patent FIXED BIRD PROOF GAPEugene J. Lehman, Zanesville, Ohio, assignor to McGraw- Edison Company,Milwaukee, Wis., a corporation of Delaware Filed Jan. 20, 1958, Ser. No.710,040

4 Claims. (Cl. 313-325) This invention relates to improvements in fixedgaps associated with electrical equipment of different potentials andmore particularly relates to isolator gaps having bird-proofing meansassociated therewith.

Lightning arresters presently in use include the socalled valve-typearrester which has included therein a plurality of totally enclosedseries spark gaps. For various reasons, it is desirable in manyapplications not to rely upon these internal gaps for the entireisolation of line voltage between the arrester and the equipment to beprotected. Thus, it has been the practice heretofore to provide an openair gap (spaced electrodes) between the line terminal of the arresterand the line terminal of, for example, a transformer. Open gaps of thetype aforementioned are susceptible to shorting by birds and mammals,etc. which deleteriously affect the coordination of the arrester and theequipment to be protected. Further, open gaps of the type noted aresusceptible to much variation in dimension in ordinary field mounting,said variations in and of themselves being undesirable because of thechanges in electrical characteristics occasioned thereby.

It is an object of this invention to provide an external isolator gapfor two pieces of the electrical equipment having a different electricalpotential, said gap maintaining the factory pre-set gap dimensionindependent of field mounting irregularities or the like.

It is another object of this invention to provide a protected isolatorgap for use as aforementioned which has the major advantages of an opengap and eliminates the disadvantages of a totally enclosed gap.

Another object of this invention is to provide an isolator gap asaforementioned wherein a pair of gap electrodes are fixedly mounted in ahorizontally aligned position within a protective enclosure whereby saidgap electrodes cannot weld together under excessive arcing conditionssince the molten metal evolved under those arcing conditions will dropdownwardly under the influence of gravity.

It is another object of this invention to provide a protective enclosureor housing for the fixed spaced electrodes forming the gap, saidenclosure having open ends which are vertically aligned whereby thecleansing action of the weather will tend to keep the gap area free ofcontamination.

Another object of this invention is to provide an isolator gap of thetype aforementioned wherein the enclosure means may take, for example,the form of a prolated ellipsoid, the ends of which are open and themarginal surfaces are irregularly shaped so as to discourage theperching of birds and small animals to thereby prevent a short circuitbetween the spaced electrodes.

A further object of the invention is to provide a protected isolator gapas aforedescribed wherein the electrical connectors connecting the fixedgap electrodes to the two pieces of electrical apparatus are so arrangedso that the mechanical forces upon one of the pieces of electricalapparatus will not be transmitted to the other Patented Oct. ll, 1960piece of electrical apparatus along at least one of said conductors,thereby eliminating stresses and breakage that might be caused by adifferent rate of expansion and contraction of the components of the twopieces of apparatus and/or to prevent the transmission of shocks thatmight occur during the shipment of the two pieces of apparatus whenassembled together for shipment as a unit.

Another object of this invention is to provide protective housing orenclosure means for an isolator gap which is made of high dielectricmaterial, is corrosion resistant, has high manufacturing tolerances, isreadily produced by mass production techniques, and is otherwise welladapted for the purposes for which it was designed.

The novel features that are characteristic of the invention are setforth with particularity in the appended claims. The invention itself,both as to its organization and its method of operation, together withadditional objects and advantages thereof, will best be understood bythe following description of a specific embodiment when read inconnection with the accompanying drawings in which:

Fig. l is a fragmentary front plan view of two pieces of electricalequipment having the novel isolator gap assembly mounted therebetween;

Fig. 2 is an enlarged top view of the isolator gap assembly shown inFig. 1;

Fig. 3 is a front plan view partially in section of the isolator gapassembly shown in Figs. 1 and 2;

Fig. 4 is a sectional view along lines 4-4 of Fig. 2; and

Fig. 5 is a sectional view of an alternative embodiment.

While the novel isolator gap assembly will be described in connectionwith its application between line terminal bushing of a transformer andan associated lightning arrester, it will become apparent that theisolator gap assembly may have a larger field of application and, hence,the scope of the claims is not to be limited to the precise descriptionof the environmental surroundings.

Returning now to Fig. 1, a transformer tank 10, normally grounded at G,has an upwardly protruding terminal assembly 11 which is connected toline voltage conductor 16 by a suitable transformer bushing connectorcap and guard assembly 12. A more detailed description of the terminalconnector and guard assembly 12 is set forth in my copending applicationhaving Serial No. 614,905, filed October 9, 1956, and assigned to thesame assignee. For purposes of the present application, the terminalconnector and guard assembly have been modified slightly to provide anaperture and auxiliary terminal lug 15 for connecting a connector 24which leads to the isolator gap assembly 30 as shall be explainedhereinafter. The lug 15 is in direct electrical connection with the linevoltage conductor 16.

A lightning arrester 13, here shown of the general type known as a valvearrester, is mounted upon the transformer tank 10 by suitable mountingmeans 14. The line terminal end of the lightning arrester has a terminallug 17 which is adapted to fixedly mount the isolator gap assembly 30between the lightning arrester l3 and transformer 10 as shall now bedescribed.

The isolator gap assembly 3t) comprises a rigid elongated conductormember 18 which may be of, for example, strap copper or the like, whichis apertured at one end to fit over and be mounted on the terminal lug1.7 of the lightning arrester 13. Fixedly mounted at the other end ofthe strap-like conductor 18 is a high dielectric protective enclosure orhousing means 19 which may be made of material such as electrical gradeporcelain or the like which encloses and protects a pair of spacedfixedly disposed electrodes 21 and 22 which are horizontally alignedwithin the enclosure means 19. The electrode 21 is attached to and maybe integral with the conductor 18 and electrode 22 in the terminal endof conductor 24 which is connected to log 15 on the transformer bushingterminal connector means 12.

The housing or enclosure means 19 may be of the general shape of aprolated ellipsoid or a sphere, the ends of which are open as shown at25 and 26, said openings 25 and 26 being vertically aligned one with theother. The upper and lower openings 25 and 26 are preferredly irregularin shape so as to afford an insecure perch for birds and small animalswhich otherwise might tend to perch thereon.

It will be observed that the enclosure means 19 when viewed as in Figs.1 and 3 shows that the sidewalls defining the openings 25 and 26 attheir lowest point such as 27 are still above the horizontally alignedelectrodes 21 and 22. The reverse is true of the sidewalls definingaperture 2.6, namely, that point 28 is substantially below electrodes 21and 22. Thus, substantial protection for the electrodes is providedagainst wind driven rain or snow, etc., while at the same timepermitting water to go down through the openings 26 and 27 to cleansethe interior of the enclosure 19. The electrodes 21 and 22 arepreferredly fixedly mounted in the sidewalls of the enclosure means 19in horizontal alignment, the gap dimension therebetween preferably beingfactory preset and, hence, not subject to variation as may occur by thenormal prior art processes. Further, the horizontal alignment ofelectrodes 21 and 22 ensures that molten metal from the electrodesoccasioned by an exceedingly heavy surge arc will tend to falldownwardly and out and, hence, the molten metal will not weld togetherthe electrodes 21 and 22.

As best shown in sectional view Fig. 4, the eletcrodes 21 and 22 arefixedly disposed in bore 33 formed centrally of opposed inwardly andoutwardly extending bosses 31 and 32, respectively, formed on each sideof the housing 19. The bores 33 may be of a substantially larger sizethan the electrodes 21 and 22 to afford sufficient tolerances necessaryfor ceramic ware if the housing is to be cast of electrical gradeporcelain. The electrodes 21 and 22 are held within their respectivebores 33 by suitable means such as lead or cement means.

It may be appropriate to note that the suggested design of the isolatorgap assembly 30, wherein the apertures 25 and 26 are of the samecontour, insures that the apertures will function equally well eventhough inverted from the position shown, that is, the aperture 25 belowand the aperture 26 above the electrodes 21 and 22.

The conductor 24 between the gap housing and the transformer bushing ispreferably made flexible, i.e., of material similar to a battery cableor the like so that any differentials in stress or shocks occasioned byexpansion and contraction of the components and/ or from shipping thecomponents in assembled relation, will not be transmitted from thetransformer bushing 11 to the housing 19 and then to the lightningarrester 13. This prevents breakage of the components. It is to be notedthat the conductor 24 is provided with suitable insulation 20 to preventa short between portions of different electrical potential.

An alternative housing 30' is shown in Fig. which is generally similarto that shown in Figs. 1-4. The major difii'erences are that thesidewalls 35 are straight rather than curvilinear and thus are adaptedto a moulding operation of, for example, fiber glass or other suitabledielectric material. It is to be noted in this embodiment that theelectrodes 21 and 22' may be directly moulded into bosses 31' and 32'.

Although a specific embodiment of the invention has been shown anddescribed, it is with full awareness that many modifications thereof arepossible. The invention, therefore, is not to be restricted exceptinsofar as neces- '4 sitated by the prior art and by the spirit of theappended claims.

What is claimed as the invention is:

:1. An external bird proof opened isolator gap adapted to isolate avalve type lightning arrester assembly from electrical apparatus withwhich said lightning arrester assembly is associated, said isolator gapcomprising first and escond electrical conductors, said first conductorbeing connected at one end to an external open line terminal on saidlightning arrester and the other end terminating in a firstsubstantially horizontal electrode, said second conductor having an endconnected to a line terminal on said eletcrical apparatus and the otherend terminating in a second substantially horizontal electrode spacedfrom said first electrode, said second conductor having a flexibleportion intermediate the ends thereof, and bird-proof enclosure meanssurrounding said first and second enclosure means having high side wallsto form a hollow housing having a vertical opening with an axis passingbetween the spaced ends of said first and second electrodes to exposesaid ends to the atmosphere, the upper surface of said housing formingan edge which has at least one vertical concavity disposed adjacent avertical plane passing through said gap to provide points whichdiscourage roosting thereon so that adjacent points of said edge lie indifferent horizontal planes to provide a minimum of horizontal surfaceupon which animals and birds may be supported.

2. An external bird proof isolator gap adapted to isolate a valve typelightning arrester assembly from electrical apparatus with which saidlightning arrester assembly is associated, said isolator gap comprisingfirst and second horizontally extending electrical conductors, saidfirst conductor being connected at one end to an external open lineterminal of said lightning arrester and the other end terminating in afirst horizontally extending electrode, said second conductor having anend connected to a line terminal of said electrical apparatus and theother end terminating in a second horizontally extending electrodespaced from said first electrode to provide a horizontal air-gaptherebetween, one of said first and second conductors having a flexibleportion intermediate the ends thereof to prevent transmission ofmechanical forces therealong, and bird proofing enclosure meanssurrounding said horizontally spaced first and second electrodes forrigidly maintaining the horizontal air-gap therebetween, said enclosuremeans being vertically perforated to provide a vertical opening havingan axis passing through said air-gap and exposing said first and secondelectrodes and the gap therebetween to the cleansing effects of theatmosphere, said housing having an upper end surface formed as ahorizontally irregular edge with at least one valley therein to providepoints which discourage roosting thereon, the floor of said beingadjacent a vertical plane passing through said gap to provide a minimumof horizontal surface for the support of birds and animals in thegeneral region of said gap.

3. A protective outdoor gap for electrical equipment, said gapcomprising a first horizontal electrode, a second horizontal electrodehorizontally spaced from said first electrode, means for electricallyconnecting said first electrode to a first electrical device, means forelectrically connecting said second electrode to a second electricaldevice, and a housing of electrical insulating material surrounding saidfirst and second electrodes and the gap therebetween, said housinghaving a perforation with an axis which passes through said gapvertically to expose said first and second electrodes to the atmosphere,the top end of the walls of said housing forming an edge having avertical dip adjacent a vertical plane of said gap to provide pointswhich discourage roosting and being sloped with respect to the horizonto provide substantially no horizontal surfaces in the region of saidhorizontal gap.

4. In combination a first horizontally disposed electrode, a secondhorizontally disposed electrode horizontally spaced from said firstelectrode, means for electrically connecting said first electrode to afirst electrical device, means for electrically connecting said secondelectrode to a second electrical device, one of said first and secondconnecting means being flexible, and a hollow housing of electricallyinsulating material surrounding said first and second electrodes and thegap therebetween, said housing having a vertical perforation with anaxis passing through said gap to expose said electrodes to the cleansingefiects of the atmosphere and being formed with at least one depressionin its top surface adjacent the vertical plane of said gap to providepoints which discourage roosting, said surface being sloped with respectto the horizontal to eliminate horizontal surfaces therefrom.

References Cited in the file of this patent UNITED STATES PATENTS470,772 Wurts Mar. 15, 1892 1,277,978 Martin et al. Sept. 3, 19181,652,990 Golladay Dec. 13, 1927 2,392,342 Steinmayer Jan. 8, 19462,469,215 Smith May 3, 1949 2,642,549 Pummer June 16, 1953 FOREIGNPATENTS 33,032 Switzerland Oct. 16, 1934

